In general, industrial machines and construction machines have a plurality of motion units and joint units and bearings are installed at the motion units and the joint units, and typically, a shaft 20 and a sliding bearing 10, which encircles the shaft, are installed at a shaft rotating unit or the joint unit (see FIG. 1).
Lubricant is supplied to the shaft 20 and a sliding bearing 10 device to allow abrasion due to friction generated during motion to be reduced.
In the sliding bearing, densification is maintained by mainly dispersing a large amount of soft copper (Cu) particles on martensite formed of iron (Fe), and in a case in which a lubricating film is broken in a sliding condition of high surface pressure and high temperature, the bearing causes a seizure due to friction with the shaft, which is a counterpart material and made of an iron (Fe) based alloy.
For example, in a case of heavy equipment such as construction machines, high surface pressure is applied to the sliding bearing, and particularly, high surface pressure is applied at the time of motion at a low speed.
When the high surface pressure is applied, the abrasion or the seizure of the sliding bearing may occur due to the friction, as described above.
Therefore, a bearing having excellent abrasion resistance and a good lubrication characteristic is used as a sliding bearing, and lubricant or grease having high viscosity is supplied to a sliding surface where the shaft and the sliding bearing are in contact.
In the related art, a brass or iron based bearing has been mainly used as the sliding bearing, and in recent years, and in recent years, an oilless type of sliding bearing is introduced and used which is able to reduce frictional resistance without frequently supplying lubricant by manufacturing the sliding bearing as a sintered body and then impregnating the manufactured sliding bearing with lubricant.
Specifically, as the sliding bearing, a bearing made of a thermally treated and processed general alloy or a bearing made of a copper alloy or a copper alloy inserted with graphite as lubricant is used.
In recent years, for the purpose of improving a period of supplying lubricant and improving durability, an iron (Fe) based sintered alloy, which is impregnated with lubricant, is used.
In general, the iron (Fe) based sintered alloy sliding bearing undergoes hardening heat treatment in order to improve strength and abrasion resistance and is manufactured using a material in which the copper of about 20 wt. % is dispersed into the constitution.
As an example of the iron based sintered alloy sliding bearing, Korean Patent Application Laid-Open No. 2004-0081474 suggests a sliding bearing of which a surface shape is finished by a cutting processing in order to simplify a process of manufacturing an iron based sintered containing sliding bearing and achieve bearing performance identical to that of the related art.
Korean Patent Application Laid-Open No. 2004-0081474 is characterized in densifying a portion with depth of 10 to 60 μm from a surface layer of an inner circumferential surface and sealing a surface air hole, but a lubricant impregnation ratio is decreased by the densification of the surface layer of the inner circumferential surface and the sealing of the surface air hole, and because an unevenness line is not optimized, an effect of improving lubrication characteristics is slight.
In the above technology, compared to the related art in which only a grinding is performed, there is a difference in that the surface layer of the inner circumferential surface is densified, but the technology is the same as that of the related art in that the surface air hole is sealed, and there is an advantageous point in that lubricant is stored in a concave line according to the unevenness to be supplied to an abrasion surface, but the effect is insignificant.
For this reason, it is necessary to develop a sliding bearing which is usefully applicable to heavy equipment such as construction equipment in which high surface pressure is applied to the sliding bearing, and has an excellent lubricant impregnation ratio.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.